Method for manufacturing semiconductor chip

ABSTRACT

There is provided a method for manufacturing semiconductor chips in which the chips as many as possible are arranged on one substrate and these chips can be cut with high accuracy in a relatively simple process. For such occasion on a wafer, short sides of the semiconductor chips are laid out to be inclined at an angle of 5° or less to a crystal orientation of the wafer. Thereafter, a laser stealth dicing method is used to form a plurality of first dicing lines along long sides of the individual semiconductor chips and a plurality of second dicing lines along short sides thereof.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a method for manufacturingsemiconductor chips.

Description of the Related Art

In wafer dicing for cutting a semiconductor substrate to manufacture aplurality of semiconductor chips, there are proposed various method foravoiding harmful effects following the dicing (cutting). For example,Japanese Patent Laid-Open No. 2011-243730 discloses the structure wherefor using a C-surface of a sapphire single-crystal substrate as asurface of the substrate, the respective chips are arranged in such amanner that the cutting faces of the substrate at the wafer dicing timeintersect with any of surfaces equivalent to an M-surface of thesapphire single-crystal substrate. According to Japanese PatentLaid-Open No. 2011-243730, even in a case of using the sapphiresingle-crystal substrate, it is possible to suppress the cutting face ofeach of the chips from being inclined to the substrate surface to avoidthe reverse direction current. In addition, Japanese Patent Laid-OpenNo. 2011-243730 also discloses the structure where each of the chips isformed in a parallelogram shape to enhance a degree of freedom in theintersection angles of the two cutting faces to the M-surface.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda method for manufacturing a plurality of semiconductor chips from asingle wafer comprising the steps of: laying out the plurality ofsemiconductor chips on the wafer; forming a layer of modified regionswithin the wafer by irradiating the wafer with laser light while movingthe wafer, the forming step being a dicing line formation step forforming a plurality of first dicing lines along long sides of thesemiconductor chips and a plurality of second dicing lines along shortsides of the semiconductor chips that are shorter and more than thefirst dicing lines; and breaking the wafer along the first dicing linesand the second dicing lines, wherein the second dicing line is inclinedat an angle of 5° or less to a crystal orientation of the wafer.

According to a second aspect of the present invention, there is provideda method for manufacturing an inkjet print head for manufacturing aplurality of semiconductor chips for the inkjet print head from a singlewafer, comprising the steps of: forming energy generating elements andelectrical connection portions corresponding to the plurality ofsemiconductor chips respectively on the wafer; forming an ejectionopening formation member in which ink supply passages corresponding tothe plurality of semiconductor chips respectively are formed on thewafer; forming modified regions within the wafer by irradiating thewafer with laser light while moving the wafer, the forming step being adicing line formation step for forming a plurality of first dicing linesconsisting of layers of the modified regions along long sides of thesemiconductor chips and a plurality of second dicing lines along shortsides of the semiconductor chips that are shorter and more than thefirst dicing lines; and breaking the wafer along the first dicing linesand the second dicing lines, wherein the second dicing line is inclinedat an angle of 5° or less to a crystal orientation of the wafer.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a chip for an inkjet printhead;

FIG. 2 is a diagram illustrating a general layout example of a pluralityof print element substrates in a wafer;

FIG. 3 is a diagram illustrating a layout example in a case ofmanufacturing the print element substrates as many as possible;

FIG. 4 is a diagram illustrating an irradiation state of laser light ina laser stealth dicing method;

FIGS. 5A and 5B are enlarged views illustrating dicing lines;

FIG. 6 is a diagram illustrating crystal orientations of a wafer;

FIGS. 7A and 7B are diagrams each illustrating a cutting state dependingon the crystal orientation;

FIGS. 8A and 8B are diagrams each illustrating a layout of a crystalorientation and print element substrates; and

FIGS. 9A and 9B are diagrams each illustrating a layout of a crystalorientation and print element substrates.

DESCRIPTION OF THE EMBODIMENTS

Incidentally in the conventional method as described in Japanese PatentLaid-Open No. 2011-243730, when each of the chips is formed in either asquare shape or parallelogram shape, the chips are generally arranged ina lattice shape to form a matrix horizontally and vertically.Accordingly the cutting lines for separating them are made by acombination of a group of straight lines in parallel to each other and agroup of straight lines in parallel to each other that intersecttherewith, and therefore the cutting process is relatively simple.

However, in a case of manufacturing more chips from a single substrate,these chips are in most cases arranged to be shifted from each other inrows or in columns. Therefore, the cutting line in at least onedirection becomes non-continuous to make the dicing process complicated,thus degrading the productivity or damaging the smoothness of thecutting face in some cases.

The present invention is made in view of the foregoing problems. Anobject of the present invention is to provide a method for manufacturingsemiconductor chips in which while chips as many as possible arearranged on a single substrate, it is possible to cut these chips withhigh accuracy in a relatively simple process.

FIG. 1 is a perspective view illustrating a chip 20 for an inkjet printhead manufactured according to the present invention. In the chip 20 anejection opening formation member 15 is formed on a print elementsubstrate 11 (semiconductor chip) made up of a silicon substrate, forexample. The print element substrate 11 is provided with a plurality ofenergy generating elements 12 and electrical connection portions 16 forsupply of power to the energy generating elements 12. An example of theenergy generating element may include a heat generating resistiveelement or piezo element. On the other hand, the ejection openingformation member 15 is provided with a plurality of ejection openings 14and ink supply passages 15 for introducing ink to the ejection openings14 respectively. The ejection opening formation member 15 is formed onthe print element substrate 11 such that the individual energygenerating elements 12 correspond to the ejection openings 14 on aone-on-one basis, thus configuring the chip 20 for the inkjet printhead. When the voltage is applied to the individual energy generatingelements 12 according to image data in this configuration, the energy isgiven to inks in contact with the energy generating elements 12, thusejecting the inks as droplets from the ejection openings 14. The printelement substrate 11 is formed as a parallelogram shape having longsides L1 and short sides L2.

The energy generating elements 12 and the electrical connection portions16 are patterned on one sheet of wafer to form the ejection openingformation member 15, which is then diced, thus manufacturing theplurality of chips 20 simultaneously.

FIG. 2 is a diagram illustrating a general layout example of theplurality of print element substrates 11 on a wafer 10. Theparallelogram print element substrates 11 are laid out as illustrated inthe figure, each having long sides L1 in parallel to Y axis and shortsides L2 in parallel to a straight line M inclined at an angle α of 59°to Y axis on an XY plane on a basis of a notch 3.

In such a layout, the individual print element substrates 11 can beseparated in the X direction by dicing (for example, ten times of dicingin FIG. 2) along dicing lines A1 in parallel to Y axis. Further, theindividual print element substrates 11 can be separated in the Ydirection by dicing (for example, nine times of dicing in FIG. 2) alongdicing lines B1 in parallel to the straight line M. Since any of thedicing lines is made up of a straight line, it is possible to adopt ageneral blade dicing method.

FIG. 3 is a diagram illustrating a layout example of a case ofmanufacturing print element substrates 11 as many as possible from thesingle wafer 10 without changing an orientation of each of the printelement substrates 11. The orientation of each of the print elementsubstrates 11 is equal to that in FIG. 2, and the long sides L1 arearrayed continuously along Y axis, but the short sides L2 are notarrayed continuously along the straight line M.

In such a layout, the individual print element substrates 11 can beseparated in the X direction by dicing (for example, 19 times of dicingin FIG. 3) along first dicing lines A2 in parallel to Y axis. However,second dicing lines B2 for separation in the Y direction each are notcontinuous in the direction of the straight line M, and are formed as azigzag route. Therefore in the present invention, not the conventionalblade dicing method but a laser stealth dicing method is adopted in thedicing line formation.

The laser stealth dicing method is a method in which laser light iscollected in an object lens optics system and a wafer is irradiated withthe collected laser light along a predetermined dicing line to formmodified regions low in crystal strength in a wafer layer and then thewafer is cut (broken) on the basis of the region. Since the dicing linecan be formed in non-contact with the wafer, a degree of freedom inshape and layout of the individual chips (print element substrates 11)can be more enhanced as compared to the blade dicing method.

FIG. 4 is a diagram illustrating an irradiation state of the laser lightin the laser stealth dicing method. In a state where the ejectionopening formation member 15 is directed toward a dicing stage 100, thewafer 10 is mounted on the dicing stage 100, and a dicing tape 103 isattached on the wafer 10 from the backside for fixation. Further, thewafer 10 is irradiated with laser light 101 in such a manner as to becollected within the wafer 10 in predetermined depths, thus formingmodified regions 102 in the predetermined depths. On the other hand, thedicing stage 100 is movable on a plane vertical to the irradiationdirection of the laser light 101. In addition, by performing anirradiation scan for irradiating the wafer with the laser light 101 in apredetermined cycle while moving the dicing stage 100 in a predeterminedspeed, it is possible to form a layer 104 of the modified regions wherethe modified regions 102 are arrayed in the predetermined depth withinthe wafer.

It should be noted that a plurality of such layers of the modifiedregions can be formed within the wafer by a plurality of irradiationscans having different focus distances of the laser light 101. Inaddition, as the number of the layers 104 of the modified regions ismade more, the number of times of the irradiation scans becomes themore, but it is possible to improve the efficiency in breaking andcertainty in cutting. At this time, the number of the layers 104 of themodified regions can be adjusted appropriately according to variousfactors in addition to the thickness of the wafer 10 or the intensity ofthe laser light 101. Here, the thickness of the wafer 10 is set to 0.625mm, and FIG. 4 illustrates a state of performing the irradiation scanfor the modified regions 102 in the second layer. The dicing line isformed by the layer of these modified regions. That is, the layer of themodified regions becomes the dicing line.

FIGS. 5A and 5B are diagrams each illustrating dicing lines B2, that is,the irradiation routes of the laser light 101 for separation in the Ydirection of the print element substrates 11 laid out as in FIG. 3. Thedicing line B2 is not continuous along the straight line M, but is azigzag route. Therefore the irradiation route of the laser light 101also has first sections 8 in parallel to the straight line M and secondsections 9 in parallel to a first dicing line A2 that are alternatelyarranged. At this time, when the irradiation of the laser light 101 isperformed along the second zigzag dicing line B2, the moving speed ofthe dicing stage 100 varies between the first section 8 and the secondsection 9. Further, there are some cases where array pitches of themodified regions 102 do not become constant and the cutting faces aftercutting the wafer 101 become non-uniform.

Therefore the first section 8 and the second section 9 are irradiatedwith the laser light 101 by different irradiation scans. Specifically asillustrated in FIG. 5B, the irradiation scan of the laser light 101 ismade to differ for each position along the short sides of the individualprint element substrates 11. That is, in a case of FIG. 5B, ten times ofthe irradiation scans along the short sides L2 (second dicing line B3)are necessary for cutting the individual print element substrates 11 toeach other in the Y direction. On the other hand, in regard toseparation of the long sides, as similar to the case of FIG. 5A, theirradiation scan is performed along the first dicing line A2. By doingthis, in both of the cutting between the short sides L2 and the cuttingbetween the long sides L1, the speed of the irradiation scan on thewafer 10 can be held constant to array the modified regions 102 in aconstant pitch.

On the other hand, the state of the cutting face depends also on thecrystal orientation of the wafer 10. FIG. 6 is a diagram illustratingthe crystal orientations of the wafer 10. The wafer 10 has A axis of thecrystal orientation <110>, B axis vertical to A axis, and C axis and Daxis of the crystal orientation <100> respectively meeting A axis and Baxis at angles of ±45°. The notch 3 is formed in the wafer 10 such thatA axis of the crystal orientation <110> is in parallel to Y axis.

FIGS. 7A and 7B are diagrams for comparing the respective states betweena case where the cutting direction conforms to the crystal orientationand a case where it does not conform thereto. The irradiation scansexplained in FIG. 4 are performed, and the plurality of layers 104 ofthe modified regions are laminated within the wafer 10 in the depthdirection. Here, there is illustrated a case where the lamination numberis six.

In a case where the cutting face conforms to the crystal orientation,the modified region 102 is inclined to easily extend in the thicknessdirection of the wafer 10 and the resistance at the cutting is small.Therefore a smooth cutting face can be obtained as illustrated in FIG.7A. In other words, so many layers 104 of the modified regions are notrequired for obtaining a preferable cutting face. On the other hand, ina case where the cutting direction is shifted from the crystalorientation, the resistance at the cutting is large, and uneven cuttingfaces are inclined to be easily formed between the layers of themodified regions as illustrated in FIG. 7B. In other words, many layers104 of the modified regions are required to be provided to some extentfor obtaining the preferable cutting face.

FIGS. 8A and 8B are diagrams each illustrating a layout state of theprint element substrates 11 relative to the crystal orientation of thewafer 10. FIG. 8A illustrates a layout in which A axis of the crystalorientation <110> is in parallel to the short side L2 of the printelement substrate 11, and FIG. 8B illustrates a layout in which B axisof the crystal orientation <110> is in parallel to the short side L2 ofthe print element substrate 11. In any case, the short side L2, that is,a second dicing line B3 is made to conform to the crystal orientation.In this way, the present invention is characterized in that thedirection of the second dicing line B3 having need of many irradiationscans each having the short distance is made to conform to the crystalorientation as much as possible. That is, the second dicing line B3 isaligned by the crystal orientation A (or B) axis. Specifically thesecond dicing line B3 is inclined at an angle of 5° or less to thecrystal orientation of the wafer, more preferably at an angle of 2° orless.

On the other hand, in regard to the first dicing line A2 having need ofa small number of times of the irradiation scans each having a longdistance, the layers 104 of the modified regions explained in FIG. 4 areformed more than those of the second dicing line B3. In a case ofperforming a small number of times of the irradiation scans each havingthe long distance, even if the number of the layers 104 of the modifiedregions increases, it is possible to suppress the tact loss to besmaller as compared to a case of performing many times of theirradiation scans each having the short distance. In this way, in regardto the second dicing line B3 possibly causing more task losses, asmoother cutting face can be realized by aligning the direction to thecrystal orientation. At the same time, in regard to the first dicingline A2 having no possibility of causing so many task losses, a smoothercutting face can be realized by forming more layers 104 of the modifiedregions. In a case where a semiconductor chip is formed in aparallelogram shape, the long side of the semiconductor chip ispreferably inclined at an angle of more than 5° to the crystalorientation of the wafer.

In the layout in FIG. 8A or FIG. 8B the print element substrates 11 areformed, and the first dicing line A2 and the second dicing line B3 areformed by a plurality of times of the irradiation scans. Thereafter, thewafer 10 is broken along the first dicing line A2 and the second dicingline B3. It is possible to manufacture the print element substrates 11each having the smooth cutting faces on both of the long side L1 and theshort side L2 simultaneously.

It should be noted that in FIGS. 8A and 8B, the print element substrates11 are laid out such that the plurality of second dicing lines B3 are inparallel to A axis of the crystal orientation <110> and B axis verticalthereto. However, the present invention is not limited thereto. Asexplained in FIG. 6, when the wafer 10 further includes C axis and Daxis of a different crystal orientation <100>, as illustrated in FIGS.9A and 9B, the print element substrates 11 may be laid out such that thesecond dicing line B3 is in parallel to C axis and D axis. Even in thelayouts as illustrated in FIGS. 9A and 9B, the effect as similar to thatin the layouts as illustrated in FIGS. 8A and 8B can be obtained byadopting the method for manufacturing the semiconductor chips asdescribed above.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2015-035744 filed Feb. 25, 2015, which is hereby incorporated byreference wherein in its entirety.

What is claimed is:
 1. A method for manufacturing a plurality ofsemiconductor chips from a single wafer comprising the steps of: layingout the plurality of semiconductor chips on the wafer; forming a layerof modified regions within the wafer by irradiating the wafer with laserlight while moving the wafer, the forming step being a dicing lineformation step for forming a plurality of first dicing lines along longsides of the semiconductor chips and a plurality of second dicing linesalong short sides of the semiconductor chips that are shorter and morethan the first dicing lines; and breaking the wafer along the firstdicing lines and the second dicing lines, wherein the second dicing lineis inclined at an angle of 5° or less to a crystal orientation of thewafer.
 2. The method for manufacturing the semiconductor chips accordingto claim 1, wherein the second dicing line is inclined at an angle of 2°or less to the crystal orientation of the wafer.
 3. The method formanufacturing the semiconductor chips according to claim 1, wherein thesemiconductor is formed in a parallelogram shape and the long side isinclined at an angle of more than 5° to the crystal orientation of thewafer.
 4. The method for manufacturing the semiconductor chips accordingto claim 1, wherein in the step for forming the dicing line, the layerof the modified regions comprises a plurality of layers laminated withinthe wafer, and the lamination number of the modified regions in thefirst dicing line is more than the lamination number of the modifiedregions in the second dicing line.
 5. The method for manufacturing thesemiconductor chips according to claim 1, wherein the crystalorientation is a crystal orientation of <110>.
 6. The method formanufacturing the semiconductor chips according to claim 1, wherein thecrystal orientation is a crystal orientation of <100>.
 7. The method formanufacturing the semiconductor chips according to claim 1, wherein thesemiconductor chip is a chip for an inkjet print head in which energygenerating elements for ejecting ink and supply passages for introducingthe ink to the energy generating elements are formed.
 8. A method formanufacturing an inkjet print head for manufacturing a plurality ofsemiconductor chips for the inkjet print head from a single wafer,comprising the steps of: forming energy generating elements andelectrical connection portions corresponding to the plurality ofsemiconductor chips respectively on the wafer; forming an ejectionopening formation member in which ink supply passages corresponding tothe plurality of semiconductor chips respectively are formed on thewafer; forming modified regions within the wafer by irradiating thewafer with laser light while moving the wafer, the forming step being adicing line formation step for forming a plurality of first dicing linesconsisting of layers of the modified regions along long sides of thesemiconductor chips and a plurality of second dicing lines along shortsides of the semiconductor chips that are shorter and more than thefirst dicing lines; and breaking the wafer along the first dicing linesand the second dicing lines, wherein the second dicing line is inclinedat an angle of 5° or less to a crystal orientation of the wafer.
 9. Themethod for manufacturing the inkjet print head according to claim 8,wherein the second dicing line is inclined at an angle of 2° or less tothe crystal orientation of the wafer.